The field of the invention is the optical packaging of laser and detector array, and in particular, the packaging of such arrays in a manner which allows them to be passively aligned accurately, so that the optical ports in the detector arrays are accurately aligned with optical fibers and input connectors.
The use of high frequency electrical-to-optical component interfaces is becoming more prevalent. One of the major problems with this type of interface, is the alignment of the optical device ports connected to optical fibers in connectors. Prior attempts to solving this problem required that special contacts and metalized features be designed into the optical chips and wire bonding, or lead frame, contacts were commonly made to the die. In addition, prior designs did not allow the user to conveniently change the plane or the orientation of the optical signal relative to the electrical signal. Other problems that existed in many of these designs were the difficulty of obtaining a predictable and reproducible separation between the emitter or detector aperture and the fiber-end coupling while maintaining high reliability under harsh, thermal, vibration, and shock environments, which increased the optical coupling losses are associated with beam divergence.
The instant invention allows for interface components such as laser array and detector array components to be passively and concurrently aligned with the fibers of a flexible optical fiber strip. For example, MT optical fiber array connectors may be employed, as shown in U.S. Pat. No. 6,056,448 issued May 2, 2000, entitled "Vertical Cavity Surface Emitting Laser Array Packaging" which is assigned to the assignee of this invention. The invention also accommodates high frequency impendance matching, and electrical-to-optical component connection through the use of precision flexible optical fiber strips The optical chips are protected by encapsulation on three sides and the optically active side being covered with the flex lamination itself. Protection of optical components with a flex circuit in an optical package, is shown in opening application Ser. No. 09/536,808 entitled "Passive Self-Alignment Technique for Array Laser Transmitters" filed by the assignee of this invention. Heat sinks can also be placed on the optical chips and exposed through encapsulation material. It also disclose an optical array chip with passive alignment in which a flexible lead sheet of a polymeric material was positioned between the optical ports of a laser or detector array and the input fibers from a connector that is connected to the package. The flexible sheet abutted against the upper ports and the fiber upper ends of the connector, so as to provide protection for them. In addition, the flexible sheet could be made of a expanded thickness in order to provide a pre-determined amount of separation between the optical ports and the fiber ends. In this manner, it would allow for the control of optical transmission characteristics such as optical coupling losses and beam divergence, in addition to providing the protection for high reliability under harsh, thermal, vibration shock environments. Optical coupling was achieved by transmission of optical signals from the connectors through the flexible circuit, which may, or may not, have holes provided in it, according to the desired optical transmission characteristics.
The present invention utilizes this same form of passive optical alignment, but provides additional advantageous features, wherein the optical component is protected with encapsulation, in addition to the protection provided by the flexible circuits. The optical array package of this invention also requires no special contacts or lead frame features to be designed into the optical chip. It is fully protected on all four sides and no wire bonding, or lead frame contacts need be made directly to the die. In addition, heat sinks can be integrated into the chip package and exposed to the encapsulation. Also, if desired, a semi-conductive circuit chip 96 may also be incorporated into the package, as shown in FIG. 11, by utilizing the same processing techniques employed to attach the dies 16 and 18 to the flex circuit. The design of the optical array package is such that is suitable for low cost, high volume manufacturing, especially for applications where high frequency impendance is required.